John,

First, Samuel T. Williams was a regular southern soldier, and not a guerrilla; so I am outside my area of knowledge. I tackled this puzzle because I know you, and because I figured it out with help from:
-- Jim McGhee's 2008 "Guide to Missouri Confederate Units, 1861-1865";
-- Peterson, McGhee, Daleen, and Lindberg's "Sterling Price's Lieutenants"; and from
-- the Missouri State Archives, military service records online.

Forget the 86th Regiment mention. It doesn't belong anyplace in this man's record, and I cannot explain why it was placed on his tombstone. The only 86th regiment of anything in MO CW was the Union 86th Enrolled Missouri Militia, which was an Adair County unit. Adair County in NE MO was far, far, away from Williams' home and the area from which he enlisted in the southern cause, which was in south-central MO. If the notation 86th has any bearing at all, perhaps Williams' was in grave number 86 in Heaton Cemetery, or something else that had nothing to do with his CW service.

Williams' Confederate pension application was short, but correct about his actual CW service on the southern side, as far as I can tell. I was unable to locate in MO State Archives a record for Samuel Thomas Williams or any similar name in the Missouri State Guard of 1861, however, so the pension application is all we have. Williams served in the 2nd Infantry Regiment, 7th Division, Missouri State Guard, and that regiment is credited with service at the battles of Wilson's Creek, Dry Creek (Vernon County), and the Lexington Siege. The 2nd Infantry of the south-central MO 7th Division, MSG was put together mostly in Oregon and Howell Counties, contained Companies A through H and another unlettered company, was commanded by Colonel John A. Foster (elected 8 July 1861, and mortally WIA at Wilson's Creek). That portion of the pension application that applies to his 1861 service applies only to the 2nd MO Infantry (not cavalry) Regiment, and to Williams' being at Wilson's Creek and at the Lexington siege.

Williams' next recorded southern service was in Colonel Edward Fristoe's unnumbered regiment, and we actually have an online record for this in the Missouri State Archives. Corporal S. T. Williams enlisted in Fristoe's regiment at Alton, Oregon County at unknown date (but probably in early 1864). Using the process of elimination, I guess Williams was in Company L under Captain Samuel W. Greer. In Fristoe's regt, Companies A through F were enlisted in Arkansas, and Companies G through L were enlisted in Oregon County, MO. Oregon County in early 1864 seemed to be the south Missouri county the furthest away from any Union outpost or garrison, and there were only occasional large Union patrols that were daring enough to ride through Oregon County during that year. Most of the time the southern men in Oregon County who were part of the military would disperse into the woods and brush when warned another Yankee patrol would be riding through, and there were only occasional skirmishes in Oregon County, which I described in other secondary works you and I discussed recently. Refer to McGhee's 2008 work that describes Fristoe's regiment in detail, but it was at the Pilot Knob actions on 26-27 September 1864, and at Independence, Big Blue River, and Mine Creek in October 1864. Fristoe reported casualties during Price's raid of 11 KIA, 40 WIA, 20 POW, and 45 MIA, and when the raid ended Fristoe had only 175 troopers remaining in the regiment, compared to the 530 he had when Price's raid began.

Corporal Williams' record concludes with his 11 May 1865 surrender at Jacksonport, AR where he was paroled on 5 June 1865.

Therefore, his gravestone combined parts of his MSG record in 1861 and his 1864-5 record as part of Fristoe's regiment, with the strange "86th Reg" thrown in for good measure. Further, he was never in the 2nd MO Cavalry Regiment in either period, but was in the 2nd MO Infantry Regiment while in the MSG, and "Fristoe's Cavalry Regiment" later in the War. Fristoe's regiment did not have a numerical identifier.

I hope that helps.
Bruce Nichols